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STORMWATER MANAGEMENT
Green Roof Demonstration Project
3RWW has begun funding Stormwater Best Management
Practice (BMP) demonstration projects, focusing on lot-level or
Low-Impact Development (LID) projects. LID is a highly effective
strategy for controlling urban stormwater runoff.
Two primary goals of LID design are:
1. to reduce runoff volume through infiltration, retention, and
evaporation
2. to find beneficial uses for water rather than exporting it as
a waste product down storm sewers.
The net effect of using multiple LID techniques is a landscape
that is functionally equivalent to predevelopment hydrologic conditions.
The result is less surface water runoff and less pollution routed
to our local streams and rivers. LID employs lot-level techniques
that reduce the impacts of development through the use of multiple
systems that retain, detain, filter, treat, use, and reduce stormwater
runoff.
Structural stormwater BMPs can be organized into three main categories:
1. Runoff volume control that is infiltration-oriented, such as
rain gardens, infiltration basins, and porous pavement
2. Runoff volume control that is non-infiltration oriented—vegetated
roofs and rain barrels
3. Runoff quality control that is non-infiltration oriented—wetlands,
retention basins and a variety of filters.
For our area, volume control is the primary consideration, and
given our soils and topography, infiltration is a limiting factor.
Therefore, 3RWW demonstration projects are focusing on runoff volume
control that is non-infiltration oriented.
Roofs are one of the most important sources of concentrated runoff
from developed sites. Managing rooftop runoff has particular value
in urbanized settings where space for other BMPs is limited. While
rooftop runoff management is helpful in the improvement of air quality,
roof temperature regulation, and energy use reductions, as well
providing aesthetic and social benefits, the 3RWW green roof demonstration
projects have stormwater management as their primary goal. 3RWW
considered both extensive and intensive roof systems. Extensive
green roofs are ecological roof covers with limited human access
and typically have limited sectional depth with thinner and less
numbers of layers. Intensive roofs are more like the traditional
roof gardens, with deeper sectional depths, and may provide access
and recreation space.
Benefits of Green Roofs
Based on documented experience and studies, a green roof offers
several important benefits not found in conventional roofing:
• Captures and evaporates from 10 to100 percent of the precipitation
that falls on it. This reduces the volume and speed of stormwater
runoff leaving the site, helping prevent sewer overflows and protect
receiving rivers and streams.
• Lowers the temperature of stormwater runoff, which helps
maintain the cool stream temperatures needed by fish.
• Improves outdoor air quality by decreasing air temperatures
and reducing smog.
• Increases vegetation and wildlife habitat on urban sites
that typically have neither.
• Provides insulation and lowers cooling and heating costs
for the building.
• Provides an attractive alternative to a conventional roof.
• Lasts twice as long as a conventional roof, saving replacement
costs and materials
• Creates a market for recycled materials, such as compost,
mulch, soil and other
green roof components. Creates jobs in multiple industries.
3 Rivers Wet Weather requested grant applications in November 2003
for green roof demonstration projects. Request for Proposals was
issued on November 17, 2003. On February 20, 3RWW received eight
proposals totaling $2.6 million, requesting a total of $1 million
in grant funding.
The following projects were awarded grants:
• Shadyside Giant Eagle (Pittsburgh):
Renovation and expansion of an existing commercial building. Extensive
roof with five-inch growing medium using non-invasive, drought resistant
plants. Excess stormwater will be captured in cisterns and provide
grey water for other uses. 3RWW funding: $240,000
• Hammerschlag Hall/CMU (Pittsburgh):
Renovation of an existing building on the CMU campus. Click here
for a web
cam view. Click here for a photo. Extensive green roof will
collect discharge from adjacent main roof area; Pennsylvania native
plants used when possible. Click here for a photo.
3RWW funding: $25,250. Click here for a final
report.
• 213-215 E. Eighth Avenue (Homestead):
Renovation of an existing commercial /residential building on
the main street of Homestead. Extensive green roof for residents
of the lofts on the upper floors. Second side of attached building
provides control side. 3RWW funding: $66,000.
• Green
Roof Stormwater Monitoring:
In addition to funding the construction of the green roof projects,
3RWW is funding the development of monitoring protocols and programs
that will provide uniform standards to evaluate the performance
of these projects. The engineering departments of the University
of Pittsburgh and Carnegie Mellon University are working on monitoring
projects.
The project at Carnegie Mellon University titled, Development
of a Green Roof Monitoring Protocol and Green Roof Stormwater
Modeling Tool, was funded by 3RWW for $70,448.
The final
report provides a summary of the different methods,
procedures, and sensors available to monitor stomwater runoff
from conventional and green roofs. It can also be used as a guide
to determine appropriate methods, procedures and sensors for monitoring
roof runoff for different applications and roof types. The study
identified best practices currently in use in Europe and the U.S.
for monitoring stormwater retention and diversion and stormwater
quality on green roof projects, and assessing the suitability
of these monitoring practices for implementation in Pennsylvania.
The recommended methods and procedures will then be applied to
all green roof projects.
The University of Pittsburgh project titled, Green Roof
Instrumentation, Data Collection and Analysis, was funded
by 3RWW for $99,356. The measurement protocol will monitor water
quality and quantity with a combination of installed instrumentation,
sample collection and laboratory testing. Pitt is currently monitoring
the Shadyside Giant Eagle green roof. To follow the project's
progress, visit Pitt's
civil and environmental engineering web site.
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